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BARNYARD MANURE AND THE MAINTE
NANCE OF FERTILITY
Manure as a Crop Producer.—Some difference of opinion exists among farmers as to the relative value of barnyard manure and commercial fertilizers for crop production, but it is worthy of note that those who are most diligent in caring for the manure have most faith in its worth as a fertilizer. The fact that barnyard manure has been used so universally by agriculturalists for so many centuries is one of the strongest arguments in its favor. That the popular estimate of its value is established by scientific experiment is well shown by investigations carried on at Rothamsted. On certain plots, as has been mentioned, crops have been grown continuously with no fertilizer of any kind added, on other plots barnyard manure at the rate of 14 tons to the acre has been used every year, and on still others various combinations of commercial fertilizers have been tested. The following table gives the yields of barley and wheat from the unmanured plots, the plots dressed with barnyard manure, and the highest results obtained from the use of any combination of fertilizing materials. The tests extend over 40 years, but to shorten the table the results are given here in averages for five eight-year periods. (Fractions have been omitted.)
It will be seen that while both the fertilized plots gave much larger yields than the one receiving no addition of plant food, there is practically no difference between the plots dressed with barnyard manure and the best commercial fertilizers. This test is hardly fair to the barnyard manure as the quantities of commercial fertilizers applied were far in excess of anything used in general practice; the amount of nitrogen added to the wheat, for instance, being equivalent to that contained in 800 pounds of nitrate of soda, which would cost practically as much as the wheat would bring on the market. In all probability, if these experiments had been conducted in this country the showing would have been more favorable to barnyard manure. It has been explained that the materials in the manure must undergo nitrification before the nitrogen
becomes available to the plants and this process takes place so much more rapidly in this country than in England that it is easy to believe better returns might be obtained from barnyard manure under American conditions.
Lasting Effect of Manure.—Barnyard manure differs from other fertilizers in its lasting effect when applied to the soil. At Rothamsted, in connection with the above experiment, one plot was manured annually for 20 years and then received no manure for the next 20 years. In the accompanying table are given the yields of barley in averages for five year periods on the plot which was never manured, and the plot that had been manured the previous 20 years. The figures given for the second plot represent the effect of the residual manure, as no fertilizer was added during the period covered by the table.
Every year Manure
Average (20 yrs.) . . . . . 13.25
The table shows that the effect of the manure was perceptible in yield for at least 20 years after the last application. It is more than likely that the more rapid rate of nitrification in this country might materially shorten the period in which the lasting effect of the manure would be observable, and perhaps the influence of the residual manure would have disappeared in a shorter time than twenty years.
Barnyard Manure the Best Fertilizer.—When everything is taken into consideration barnyard manure, which has been properly cared for, is undoubtedly the best substance that the farmer can use as a fertilizer. It supplies all the elements of plant food, and while these are not all in forms immediately available to the plant, a comparison of manure and commercial fertilizers during a period of several years is practically
always favorable to the former. The value of barnyard manure cannot be estimated from the content of nitrogen, phosphoric acid and potash alone, for it is probably as valuable on account of its effect on the physical condition of the soil as for the plant food which it contains. It has no equal among fertilizers as a humus former, and the usefulness of humus in improving the tilth of the soil and increasing its power to hold water was explained in an earlier chapter.
The use of the animal excrements is also beneficial because it increases the desirable fermentations, or
bacterial action, in the soil. In fact it seems certain that the farmer would be well repaid for applying the manure for its indirect effect in improving the condition of the soil, even though it contained none of the elements of plant food.
Barnyard manure is also the safest fertilizer to use especially by the inexperienced farmer or the one who is careless in his methods. There is little danger of
lasting injury to the soil from the use of manure, while it is possible to use commercial fertilizers in such a way as to make the soil poorer after their use than it was before.
Relation of Manure to Maintenance of Fertility.The discovery of the fact that fully 80 per cent. of the fertilizing constituents of the crop can be recovered in the manure has thrown a new light on the subject of the maintenance of fertility. A number of the most prominent authorities on agriculture believe (and the belief seems perfectly plausible in view of the facts